(01-30-2017, 04:17 AM)fixkick Wrote: what dont we know.?
well fuel pressure
nor if other DTCs are tripping, (not seen , live scans done hard driving and failing )
we take a car out and drive it aggressive up a hill . with the scan tool connected.
to get lean cylinders to misfire , it takes driving aggressive. (not fast speeds, but loading the engine hard over and over up a hill. you have hills? not in Kansas.
this is when the other DTC P030x codes can POP, now.
and if they did, it would speak load and clear with might be wrong.
engine lean or the other 20 year old boots bad.
since compression is ok, says the sparks bad or fueling.
try some Chevron Techron yet, in the tank additive, its got super strong benzene it it (the cheap stuff is junk at walfart, has only Stoddard solvents, useless that is)
to clean the injectors (its name is that)
misfire means lost combustion
misfire can happen too rich or too lean.
or bad spark, engine ok.
you are here asking how to test, right and not guess?
not in a shop hooked to scope and watching spark plasma , signals, all good shops can do that and see cause, of misfire
they can see the coil work, right (HV), that HV sizes and the plasma size tells them whats up. (or not)
its not coil if HV is ok, but can be bad boots, which bypasses spark plugs and the energy just jumps to the engine spark wells.
if the cylinders are lean or rich they can see that too "plasma size and shape".
(see HV here, that is good, as it he P for plasma. perfect)
http://www.jeepdied.com/scope%20views/hv-good1w.JPG
see that fuzzy line in the P, that is fuel burning, amazing no?
at home you dont have a scope or that $25 mag clamp, im using.
so can not know what's wrong, spark x4 or fuel mix wrong.
it's one or the other,
what the real question is, what costs more? guessing or 1hr shop time (diagnosis time, only)
The loss of power is a large list.
low fuel pressure (filter packed after 20 years??????)
spark misfire (a scoped test. shows this easy)
engine is good. seems so to me...
fueling wrong due to WEAK MAF sensor?, the PCM only tells you when its dead, never weak but P0171 lean, code, can happen.
When I was young , before blessed with tools, (fancy tools) I had shops use their SUN 300 ,(on up) to check for spark problems.
Some problems are not easy. (complex systems all are like that)
Some can never be found guessing, (id say 1/2) (like if you put in a bad part or its a wiring problem, or is 2 or 3 problems typically seen on most 90s cars.)
happy trails. and cheers and good luck.
http://www.fixkick.com